Plant Propagation PLS 3221/5222

Transcription

1 Plant Propagation PLS 3221/5222 Dr. Sandra Wilson Dr. Mack Thetford Chapter 2 Introduction to the Biology of Plant Propagation -A review- 1

2 The Plant Breeder and the Plant Propagator Plant Breeder, The role of the plant breeder is to recreate patterns of genetic variation in its many forms from which to select new kinds of plants useful to humans. Plant Propagator. The role of the plant propagator is to multiply these selected cultivars and to do it in such a manner as to maintain the genetic characteristics of the original population. Species The natural grouping of plants that have common characteristics in appearance, adaptation, and breeding behavior (can freely interbreed with each other). 2

3 Cultivar A group of plants that have originated in cultivation, are unique and similar in appearance, and whose essential characteristics are maintained during propagation. Chapter 2 Objectives are to Understand Alternation of generations as it relates to life cycles in plants Sexual (seed) and asexual (vegetative) propagation Seedling populations and clones How genes impact propagation Plant hormones and their role in plant development Basic life cycles of plants as related to propagation Ownership and control of cultivars 3

4 1. Alternation of Generations in Reproduction The life cycle begins with the zygote. a zygote is the single cell that results from the union of a male and female sex cell. Cell Division Mitosis is cell division in vegetative tissue (somatic), cell division for growth. Meiosis is a reductive division used during the sexual reproductive cycle to produce the gametes (male and female sex cells). 4

5 Cell cycle - period from the beginning of one cell division i i to the next. Interphase Prophase Metaphase Anaphase Telophase Meristematic Cells _bio/photos/photos/planttissue.html ag.arizona.edu/hydroponictomatoes/ tomatoz1.gif 5

6 Meiosis Prophase 1 Metaphase 1 Anaphase 1 Telophase 1 Prophase 2 Metaphase 2 Anaphase 2 Telophase 2 Meiosis genetics/meiosis.gif 6

7 Sexual reproduction Meiosis is the process that results in new patterns of genetic variation. Three opportunities for variation exist: 1. Crossing over The exchange of chromosome segments 2. The independent assortment of the chromosomes during the later stages of meiosis II (Anaphase 2) 3. The creation of new zygotes during fertilization. 7

8 2. Seedling versus Clonal Populations Seedling propagation genotype versus phenotype Genetic variation Clonal propagation Seedling Population a group of plants propagated from seed and originating ii from the same parental tlsource. Plants produced from seed are separate individuals, each with a new and unique genotype. 8

9 Genotype versus Phenotype Genotype = the total combination of genes nuclear, cytoplasmic and mitochondrial. Phenotype = the overall appearance, performance, and adaptation of a particular plant. Phenotype = Genotype + environment Genetic Variation Dominant D Recessive d Homozygous = gene pairs predominantly the same on homologous chromosomes. (DD or dd) Heterozygous = gene pairs predominantly different on Heterozygous = gene pairs predominantly different on homologous chromosomes. Dd 9

10 Genetic Variation Parental generation: DD (tall) dd (dwarf) Gametes: D d F 1 generation: Dd (tall) Inheritance involving a single pair of alleles in the gene controlling height in the garden pea. Genetic Variation Gametes from the F 1 female parent Gametes from F 1 male parent D D d DD Dd d Dd dd F 2 generation after self fertilization Three tall plants (DD Dd Dd) One dwarf plant (dd) 10

11 Genetic Variation F 2 generation after self fertilization Three tall plants (DD Dd Dd) One dwarf plant (dd) Phenotype (Genotype) Segregationwithin the F2generation two phenotypes (tall & dwarf) three genotypes (DD Dd dd) Clonal Population All members of the population have originated by vegetative tti propagation from a single plant and are expected to possess it s same genotype. This is possible because ofadventitious shoots This is possible because of adventitious shoots and roots. 11

12 Clonal Propagation natural adventitious shoot and root production Adventitious stem on roots of Ilex Adventitious roots on stem of Hoya Clonal Propagation grafting and budding Scion Root stock Joining separate stems together where one component provides the root system (root stock) and the other the shoot system (scion). 12

13 3. How genes impact Plant Propagation Provide the physical mechanisms by which individual traits and characteristics are reproduced from generation to generation both by seed (meiosis) or clones (mitosis). How genes impact Plant Propagation Genes contain the specific directions for regulating the chain of morphological and physiological events that determine the expression of specific traits and characteristics of the phenotype. 13

14 Dr. Dave Clark 4. Gene Regulation Gene Regulation Biotechnology 14